Diverse Routes for the Synthesis of Indole-Fused Complex Architecture from Simple Molecules

Several easy, efficient and convenient procedures to access indoles fused heterocyclic systems are described in this review. These heterocyclic systems were synthesized from several cyclic or acyclic molecules via a variety of reactions such as Diels-Alder reaction, Michael addition, Morita- Baylis-Hillmann reaction and many other domino/Cascade approaches with high selectivity. Most of the given protocols in this review proceed through organocatalytic pathways; however, some underwent different catalytic and non-catalytic reactions.